FIELD OF THE INVENTION
The invention relates to an apparatus for the inductive cross-field heating of flat material, including a plurality of mutually opposite induction loops being disposed above and below the flat material, some of the induction loops projecting beyond the edges of the flat material, and others of the induction loops terminating within the width of the flat material.
Such an apparatus for the inductive cross-field heating of flat material is known from Published European Application No. 0 246 660. There, an overall configuration being formed of main coils and auxiliary coils is proposed. The main coils are disposed perpendicularly to the direction of movement of the flat material and project beyond the two outer edges of the flat material. The auxiliary coils extend parallel to the direction of movement of the flat material and are disposed in the vicinity of the edges of the flat material, but without projecting beyond them. The combination of main and auxiliary coils achieves a uniform temperature profile over the entire width of the flat material. The main coils in particular heat the middle region and the two immediate edge regions of the flat material, but zones of lower temperature occur in the vicinity of the edges and parallel to them. The zones in the vicinity of the edges are reheated by the auxiliary coils, so that the necessary uniform temperature distribution is established over the entire width of the flat material.
Since the main coils and in particular also the auxiliary coils have to be matched to the width of the flat material to be heated, mechanical devices must be provided for adjusting the coil width. The auxiliary coils in particular must be capable of being matched exactly to the width of the flat material, in order to reheat the zones of lower temperatures in the vicinity of the edges and parallel thereto in the desired way. The matching of the main and auxiliary coils to the width of the flat material is complicated and labor-intensive. If a non-uniform and unsatisfactory temperature profile is measured over the: width of the flat material during the cross-field heating, no readjustment is possible during operation.